In this dissertation we present the research findings around two important hot topics of modern and future fiber-optic communication systems: 100 Gbit/s transmission and alloptical processing of received phase-modulated signals. The findings are discussed in the same chronological order they were obtained. Each topic is summarized in two chapters that correspond to one selected journal and one conference publications. The first and second chapters are dedicated to the simulation and numerical analysis of 100 Gbit/s systems. In chapter one, we present a thorough investigation of the best 100 Gbit/s serial modulation format. Seven different modulation formats are considered and are compared in terms of tolerance to dispersion and maximum reach for a 10⁻⁹ bit error rate target. In chapter two, the behavior of chapter one’s best candidate is analyzed in a realistic environment. The influence of the existing lower data rate neighboring channels is discussed in particular. The results of these two chapters were obtained in collaboration with engineers from the Deutsche Telekom Technology Center in Darmstadt, Germany. They served as a theoretical basis for a field trial carried out by this same company. Chapter three and four focus on the use of semiconductor optical amplifiers for all-optical processing applications. Impaired phased-modulated signals are under particular interest in this study. The novelty in this work resides in the counter-propagating configuration that the semiconductor optical amplifier is operated in. In chapter three we give a detailed description of the experimental results. The complete setup is explained and the improvement in Q-factor and bit error rate for the received signal is proven. Furthermore, two novel concepts (Photonic Balancing and Saturated Asymmetric Filtering) that explain the observed improvements are developed and discussed for the first time to the best of our knowledge. Finally, chapter four aims at optimizing numerically the experimental setup for the saturated asymmetric filtering technique. The required detuned filter after the saturated semiconductor optical amplifier is optimized in terms of both off set and bandwidth.